TITLE: GCN CIRCULAR
NUMBER: 11299
SUBJECT: GRB 100925A: Nearby DSS Source - SN-GRB or new Galactic transient?
DATE: 10/09/25 13:55:24 GMT
FROM: Alexander Kann at TLS Tautenburg
D. A. Kann (TLS Tautenburg) speculates:
GRB 100925A (Mangano et al., GCN 11296) is a very peculiar event. It was
an extremely long image trigger (1592 seconds), yet, after slewing to it,
Swift discovered that the X-ray afterglow is still bright. Furthermore,
looking at the Swift XRT repository page (Evans et al. 2007, 2009)
(http://www.swift.ac.uk/xrt_curves/00434928/) the source remains
constantly bright over almost 9000 seconds (two orbits).
Inspection of the DSS images of this field, using the position of the
bright UVOT transient (Marshall, GCN 11298), shows that there is what
seems to be an extended source a few arcseconds to the west (R.A.:
16:59:01.501; Dec.: -15:15:28.76 according to the native DSS WCS system).
It is clearly detected in the red frame, and more marginally in the IR
frame (DSS blue or SDSS are not available for this field). There are also
some stars nearby, but at much larger separation (> 10 arcsec). There is
no source directly beneath the UVOT position.
While the initial properties are reminiscent of two local XRFs associated
with broadlined Type Ic SNe, namely XRF 060218 (Campana et al. 2006) and
XRF 100316D (Starling et al. 2010) (the nearby DSS source being the host
galaxy), the continuing strong X-ray emission as well as the position near
the Galactic bulge (Galactic longitude 5.52, Galactic latitude 16.56) may
also point to a new Galactic source.
Spectroscopic follow-up is encouraged.
This message may be cited.